The present invention relates to an electrophotographic copying apparatus and more particularly, to an electrophotographic copying apparatus which employs copy material or copy paper in a roll form and in which turbulence or blur of copied images is advantageously prevented.
Conventionally, in the electrophotographic copying apparatuses employing copy paper in a roll form, there are two systems for achieving proper positioning of the copy paper relative to an image formed on a photosensitive drum. More specifically, in one of the systems, the leading edge of the copy paper is detected while the copy paper is being moved, and the detection signal obtained thereby is utilized for moving an original platform (or optical system), while in the other of the systems, the copy paper is first fed to a positioning device provided at a distance from the transfer position shorter than the distance between a position corresponding to start of an exposure and a transfer position for subsequent re-starting of the copy paper in synchronization with the image of an original formed on the photosensitive member.
The conventional arrangements as described above, however, have disadvantages that in the first system, since the accuracy with respect to the starting position for movement of the original platform (or optical system) directly affects the accuracy of the positioning, a special positioning device for the original platform (or optical system) is required, while in the second system, not only is a special positioning device required along the path of the copy paper, but the circuitry involved is inevitably complicated for controlling such special positioning device. Moreover, in both of the known systems as described in the foregoing, copy paper detecting means is required to be disposed in the path of the copy paper, and if a detecting device of the contact type such as a microswitch or the like is employed for the detecting means, copy paper jamming tends to be caused thereby, while employment of a detecting device of the non-contact type such as a photosensor, etc. results in high cost of the copying apparatus. Additionally, the conventional systems as described in the foregoing have a fatal disadvantage that, since cutter means is arranged to be actuated during exposure for cutting the copy paper, vibrations from the impact at the moment of cutting are undesirably transmitted to the optical systems, etc., thus giving rise to blurring or the like in the copied images. Furthermore, in a known system in which a rotary blade of the cutter means is arranged to be returned to a cutting stand-by position after the cutting by utilization of the driving force of a driving system, variation in the driving torque during winding for the returning movement also gives rise to deviation in the synchronization of the optical system, etc., with consequent adverse effects on the copied images.
Furthermore, in the known copying apparatuses of the above described type, there is incorporated a cutter operating device or more particularly, a so-called step by step cutting system by which the copy paper in roll form is cut into predetermined sizes, such as A4, B5 sizes, etc. In a copying apparatus equipped with the cutter operating device of the above described type, a cut signal for driving the cutter means is obtained by an arrangement in which the starting position of rotating cam means is altered so as to correspond to respective paper sizes for actuating stationary switch means by said cam means or by another arrangement in which a plurality of switches corresponding to respective sizes are disposed at predetermined positions around the cam means and only the switch for the size corresponding to the original being copied is made conductive. The conventional arrangements as described above, however, have disadvantages in that they have a complicated structure, thus resulting in a high cost, and particularly, in the cam rotating type, a subsequent copying operation can not be started until the cam means completes one rotation, so that the same copying time required for a large-sized original is required even for a small-sized original, with consequent reduction of the copying efficiency.